Newly released Senate legislation to curb surprise medical bills would allow third parties to settle billing disputes, a provision that could complicate passage because it is opposed by the White House and absent from a House draft.

The Senate bill represents nearly a year of work led by Sens. Bill Cassidy, R-La., and Maggie Hassan, D-N.H. If lawmakers aren’t able to resolve the differences between the two chambers and win over the White House, then a victory on healthcare that was once in sight this year may escape them.